In the field of citrus fruit processing, the application of food additive magnesium oxide as a novel solidifying agent is triggering technological innovation in the industry. This article will systematically elaborate on the innovative application of magnesium oxide in citrus fruit surface treatment from three dimensions: technical principles, application process, and quality control.
I. Mechanism of Action and Chemical Characteristics
Magnesium oxide (MgO), as an alkaline earth metal oxide, has a unique electronic configuration of magnesium ions (Mg²⁺) in its molecular structure. During citrus fruit surface treatment, Mg²⁺ specifically binds to carboxyl groups in pectin molecules, forming a stable three-dimensional network structure. Compared to traditional calcium ion cross-linking systems, this metal-pectin complex has a higher bond energy (approximately 15-20% increase), significantly enhancing the mechanical strength and thermal stability of the pectin gel.
Experimental data shows that when using a 0.3-0.5% concentration of magnesium oxide treatment solution, the pectin extraction rate of citrus peel can be increased to 92.3%, and the gel strength can reach 350g/cm² (an increase of approximately 40% compared to traditional methods). This strengthening effect stems from the dual action of magnesium oxide: on the one hand, it forms a dense structure through ionic cross-linking, and on the other hand, it adjusts the system pH to 8.2-8.5, creating an optimal environment for pectin methylesterase activation.
II. Innovative Process Flow
The new treatment process includes three key stages: pre-treatment → penetration reaction → stabilization. The specific operating parameters are as follows:
- Pre-treatment: Washing the citrus surface with 40°C warm water to remove the wax layer.
- Penetration Reaction: Immersing the fruit in a buffer solution containing 0.4% magnesium oxide (pH 8.3) and treating it at a constant temperature of 45°C for 20 minutes.
- Stabilization: After rinsing with pure water, curing under relative humidity of 65% for 12 hours.
This process maximizes pectin structure modification by optimizing the dynamic balance between ion penetration rate and reaction time. Experiments have proven that the fracture elongation of the treated citrus peel is reduced by 28%, and the compressive strength is increased by 35%, effectively improving shape retention ability in subsequent processing.
III. Quality Control System
To ensure application safety, a triple quality control mechanism is established:
- Raw Material Standard: Food-grade magnesium oxide purity ≥99.2%, lead content ≤2ppm.
- Process Monitoring: Real-time monitoring of pH fluctuation range of the treatment solution (±0.2).
- Finished Product Inspection: Residual magnesium ion content ≤150mg/kg (GB 2762 standard).
X-ray diffraction analysis shows that the pectin-magnesium complex formed on the treated citrus surface has a stable crystal structure, and the disintegration rate in simulated gastric fluid for 24 hours is less than 5%, confirming its biological safety.